Geotechnical Engg (CE-701) - Important Questions

Given bulk/moist density, water content and $G$, calculate void ratio, degree of saturation (and porosity/dry unit weight/water required for full saturation).

Draw soil phase diagram and derive the fundamental relationship $e S_r = w G$.

The dry unit weight of a soil sample in the loosest state is $13.34\text{ kN/m}^3$ and in the densest state, it is $21.19\text{ kN/m}^3$. Determine the relative density of the sand when it has porosity of $33\%$. Assume the grain specific gravity as $2.68$.

Given $D_{60}$, $D_{30}$ and $D_{10}$, determine $C_u$ and $C_c$ and classify the soil as well graded or poorly graded.

Describe IS soil classification based on grain size and explain total, neutral and effective stresses.

Given natural mass, dry mass, specific gravity and sample dimensions, determine void ratio, porosity, degree of saturation, $\gamma_{wet}$, $\gamma_d$ and $\gamma_{sat}$.

Write a short note on the pipette method.

Explain in detail about three clay minerals.

Calculate uniformity coefficient, coefficient of curvature, gradation, plasticity index, IS classification from plasticity chart, and consistency from Atterberg limits and gradation data.

Explain textural soil classification.

Calculate the effective stress at a given depth / layer interfaces for a soil profile with water table and given unit weights.

Explain flow nets, their characteristics and uses.

Calculate the average coefficient of permeability parallel and normal to flow for a stratified soil deposit.

Explain determination of coefficient of permeability by constant head method.

Define Darcy's law and discuss limitations of Darcy's law and factors affecting permeability of soil.

Describe pumping-out methods for determination of coefficient of permeability in the field, with advantages and disadvantages.

Derive the expression for the average coefficient of permeability in the horizontal direction for stratified soil.

Define quick sand condition and derive the expression for critical hydraulic gradient.

Define critical hydraulic gradient and quick sand (quick) condition.

With the help of a sketch of a flow net, derive the formula to determine the quantity of seepage through an earth dam.

Plot the variation of total stress, pore water pressure and effective stress with depth for a given soil profile and water table position.

Factors affecting the permeability / coefficient of permeability of soil

What is field compaction and what are the different methods of field compaction?

Calculate vertical stress increase at multiple points due to two surface point loads using Boussinesq's theory with superposition.

Determine vertical stress directly below and at an offset from a surface concentrated load using Westergaard's theory.

Derive Boussinesq-based vertical stress under the centre of a uniformly loaded circular area.

Explain the differences between IS light compaction and IS heavy compaction.

Compare and contrast Boussinesq's and Westergaard's theories for stress distribution.

Find vertical stress below center and corner of a uniformly loaded rectangular area using equivalent rectangles and 2:1 method.

Explain the standard Proctor test procedure for determining maximum dry density (MDD) and optimum moisture content (OMC) of soil.

Find vertical pressure at depth below center of rectangular uniformly loaded footing using equivalent point load method.

State the assumptions made in Boussinesq's equation for stress distribution in soil.

Define the compaction. How it is different from consolidation?

Differentiate between standard proctor test and modified proctor's test.

State and discuss the assumptions of Terzaghi's theory of one-dimensional consolidation and their validity.

There is a layer of soft clay 4 m thick under a newly constructed building. The overburden pressure over the center of the clay layer is 300 kN/m2. Compute the settlement, if there is an increase in pressure due to construction of 100 kN/m2. Take $C_c = 0.50$, $G = 2.70$. The water content of the deposit was found to be 50 %.

Explain any one method to compute the coefficient of consolidation.

Define coefficient of consolidation and explain its use in settlement analysis.

Given doubly drained clay thickness, final settlement and $c_v$, compute consolidation settlement versus time and plot the settlement-time curve.

Using time scaling $t \propto H^2$ for the same degree of consolidation, find field consolidation time from oedometer test time given lab and field thicknesses with same drainage conditions.

Define over consolidated, under consolidated and normally consolidated clays.

Define 'preconsolidation pressure'. In what ways is its determination important in soil engineering practice? Describe a suitable procedure for determining the preconsolidation pressure.

Given clay thickness, drainage condition, coefficient of consolidation $c_v$ and time factor $T_v$, compute the time required to attain a specified degree of consolidation / settlement using $t = T_v H^2/c_v$.

Differentiate between coefficient of consolidation vs coefficient of compressibility, coefficient of compression vs compression index, and shear strength vs shear stress.

Explain the types of shear tests based on drainage conditions (UU, CU, CD) and the significance of each drainage condition.

Methods of soil stabilization and functions and applications of geosynthetics in detail

How do soils attain their shear strength? Explain soil strength Envelope?

Types of geosynthetics used in soil engineering and their functions

Describe the direct shear test and explain its merits and demerits compared to the triaxial test

In a direct shear test on a specimen of clean dry sand, a normal stress of $180\text{ kPa}$ was applied and failure occurred at a shear stress of $100\text{ kPa}$. Determine analytically the angle of shearing resistance, the principal stresses during failure and directions of the principal planes with respect to the direction of the plane of shearing.

Describe the unconfined compression test and state the type of soil for which it is suitable

Write the different type of soil stabilization. Discuss briefly about cement stabilization.

Determine apparent cohesion and friction angle from undrained triaxial test results with given confining pressures and failure loads

Explain the phenomenon of "Liquefaction" is saturated fine sandy soil.

Function and application of geosynthetics and grain size distribution of soil

Explain any two of the following: